Hi I K,
Thanks a lot for your reply.
I really like your approach for estimating the amount of energy stored! It will save me a lot of time in the future.
However you missed a 0 in your calculation.
(10.7 x 10^15) / (3.6 x 10^12 ) = 2,972
Your estimate, which was relatively good, gives 2,972 GWh, not 297 GWh.
The estimated 1,800 GWh assumes 75% overall efficiency, a dam 350 m high (not 300 m high), a variation of 100 m in the upper reservoir and was calculated with the actual height of the reservoir, taking into account the level variation on both reservoirs. This was done in excel and the calculations assumed 10 m intervals based on the variation of the upper reservoir.
The estimation for a 300 m high dam is 1,325 GWh. I am sorry for the confusion.
I would be very interested to hear more about your other sites!